package com.jbittorrent.utilityclasses;

import java.io.*;
import java.nio.*;
import java.util.*;

/**
 * A set of utility methods to decode a bencoded array of byte into a Map.
 * integer are represented as Long, String as byte[], dictionnaries as Map, and
 * list as List.
 * 
 */
public class BDecoder {

	private boolean recovery_mode;

	public static Map decode(byte[] data)

	throws IOException {
		return (new BDecoder().decodeByteArray(data));
	}

	public static Map decode(BufferedInputStream is)

	throws IOException {
		return (new BDecoder().decodeStream(is));
	}

	public BDecoder() {
	}

	public Map decodeByteArray(byte[] data)

	throws IOException {
		return (decode(new ByteArrayInputStream(data)));
	}

	public Map decodeStream(BufferedInputStream data)

	throws IOException {
		Object res = decodeInputStream(data, 0);

		if (res == null) {

			throw (new IOException("BDecoder: zero length file"));

		} else if (!(res instanceof Map)) {

			throw (new IOException("BDecoder: top level isn't a Map"));
		}

		return ((Map) res);
	}

	private Map decode(ByteArrayInputStream data)

	throws IOException {
		Object res = decodeInputStream(data, 0);

		if (res == null) {

			throw (new IOException("BDecoder: zero length file"));

		} else if (!(res instanceof Map)) {

			throw (new IOException("BDecoder: top level isn't a Map"));
		}

		return ((Map) res);
	}

	private Object decodeInputStream(InputStream bais, int nesting)

	throws IOException {
		if (nesting == 0 && !bais.markSupported()) {

			throw new IOException("InputStream must support the mark() method");
		}

		// set a mark
		bais.mark(Integer.MAX_VALUE);

		// read a byte
		int tempByte = bais.read();

		// decide what to do
		switch (tempByte) {
		case 'd':

			// create a new dictionary object
			Map tempMap = new HashMap();

			try {
				// get the key
				byte[] tempByteArray = null;

				while ((tempByteArray = (byte[]) decodeInputStream(bais,
						nesting + 1)) != null) {

					// decode some more

					Object value = decodeInputStream(bais, nesting + 1);

					// add the value to the map

					CharBuffer cb = Constants.BYTE_CHARSET.decode(ByteBuffer
							.wrap(tempByteArray));

					String key = new String(cb.array(), 0, cb.limit());

					tempMap.put(key, value);
				}

				bais.mark(Integer.MAX_VALUE);
				tempByte = bais.read();
				bais.reset();
				if (nesting > 0 && tempByte == -1) {

					throw (new IOException(
							"BDecoder: invalid input data, 'e' missing from end of dictionary"));
				}
			} catch (Throwable e) {

				if (!recovery_mode) {

					if (e instanceof IOException) {

						throw ((IOException) e);
					}

					throw (new IOException(e.toString()));
				}
			}

			// return the map
			return tempMap;

		case 'l':

			// create the list
			List tempList = new ArrayList();

			try {
				// create the key
				Object tempElement = null;
				while ((tempElement = decodeInputStream(bais, nesting + 1)) != null) {
					// add the element
					tempList.add(tempElement);
				}

				bais.mark(Integer.MAX_VALUE);
				tempByte = bais.read();
				bais.reset();
				if (nesting > 0 && tempByte == -1) {

					throw (new IOException(
							"BDecoder: invalid input data, 'e' missing from end of list"));
				}
			} catch (Throwable e) {

				if (!recovery_mode) {

					if (e instanceof IOException) {

						throw ((IOException) e);
					}

					throw (new IOException(e.toString()));
				}
			}

			// return the list
			return tempList;

		case 'e':
		case -1:
			return null;

		case 'i':
			return new Long(getNumberFromStream(bais, 'e'));

		case '0':
		case '1':
		case '2':
		case '3':
		case '4':
		case '5':
		case '6':
		case '7':
		case '8':
		case '9':

			// move back one
			bais.reset();

			// get the string
			return getByteArrayFromStream(bais);

		default: {

			int rem_len = bais.available();

			if (rem_len > 256) {

				rem_len = 256;
			}

			byte[] rem_data = new byte[rem_len];

			bais.read(rem_data);

			throw (new IOException("BDecoder: unknown command '" + tempByte
					+ ", remainder = " + new String(rem_data)));
		}
		}
	}

	private long getNumberFromStream(InputStream bais, char parseChar)
			throws IOException {
		StringBuffer sb = new StringBuffer(3);

		int tempByte = bais.read();
		while ((tempByte != parseChar) && (tempByte >= 0)) {
			sb.append((char) tempByte);
			tempByte = bais.read();
		}

		// are we at the end of the stream?
		if (tempByte < 0) {
			return -1;
		}

		return Long.parseLong(sb.toString());
	}

	// This one causes lots of "Query Information" calls to the filesystem
	private long getNumberFromStreamOld(InputStream bais, char parseChar)
			throws IOException {
		int length = 0;

		// place a mark
		bais.mark(Integer.MAX_VALUE);

		int tempByte = bais.read();
		while ((tempByte != parseChar) && (tempByte >= 0)) {
			tempByte = bais.read();
			length++;
		}

		// are we at the end of the stream?
		if (tempByte < 0) {
			return -1;
		}

		// reset the mark
		bais.reset();

		// get the length
		byte[] tempArray = new byte[length];
		int count = 0;
		int len = 0;

		// get the string
		while (count != length
				&& (len = bais.read(tempArray, count, length - count)) > 0) {
			count += len;
		}

		// jump ahead in the stream to compensate for the :
		bais.skip(1);

		// return the value

		CharBuffer cb = Constants.DEFAULT_CHARSET.decode(ByteBuffer
				.wrap(tempArray));

		String str_value = new String(cb.array(), 0, cb.limit());

		return Long.parseLong(str_value);
	}

	private byte[] getByteArrayFromStream(InputStream bais) throws IOException {
		int length = (int) getNumberFromStream(bais, ':');

		if (length < 0) {
			return null;
		}

		// note that torrent hashes can be big (consider a 55GB file with 2MB
		// pieces
		// this generates a pieces hash of 1/2 meg

		if (length > 8 * 1024 * 1024) {

			throw (new IOException("Byte array length too large (" + length
					+ ")"));
		}

		byte[] tempArray = new byte[length];
		int count = 0;
		int len = 0;
		// get the string
		while (count != length
				&& (len = bais.read(tempArray, count, length - count)) > 0) {
			count += len;
		}

		if (count != tempArray.length) {
			throw (new IOException(
					"BDecoder::getByteArrayFromStream: truncated"));
		}

		return tempArray;
	}

	public void setRecoveryMode(boolean r) {
		recovery_mode = r;
	}

	private void print(PrintWriter writer, Object obj) {
		print(writer, obj, "", false);
	}

	private void print(PrintWriter writer, Object obj, String indent,
			boolean skip_indent) {
		String use_indent = skip_indent ? "" : indent;

		if (obj instanceof Long) {

			writer.println(use_indent + obj);

		} else if (obj instanceof byte[]) {

			byte[] b = (byte[]) obj;

			if (b.length == 20) {
				writer.println(use_indent + " { " + b + " }");
			} else if (b.length < 64) {
				writer.println(new String(b));
			} else {
				writer.println("[byte array length " + b.length);
			}

		} else if (obj instanceof String) {

			writer.println(use_indent + obj);

		} else if (obj instanceof List) {

			List l = (List) obj;

			writer.println(use_indent + "[");

			for (int i = 0; i < l.size(); i++) {

				writer.print(indent + "  (" + i + ") ");

				print(writer, l.get(i), indent + "    ", true);
			}

			writer.println(indent + "]");

		} else {

			Map m = (Map) obj;

			Iterator it = m.keySet().iterator();

			while (it.hasNext()) {

				String key = (String) it.next();

				if (key.length() > 256) {
					writer.print(indent + key.substring(0, 256) + "... = ");
				} else {
					writer.print(indent + key + " = ");
				}

				print(writer, m.get(key), indent + "  ", true);
			}
		}
	}

	private static void print(File f, File output) {
		try {
			BDecoder decoder = new BDecoder();

			decoder.setRecoveryMode(false);

			PrintWriter pw = new PrintWriter(new FileWriter(output));

			decoder.print(pw, decoder.decodeStream(new BufferedInputStream(
					new FileInputStream(f))));

			pw.flush();

		} catch (Throwable e) {

			e.printStackTrace();
		}
	}

	public static void main(String[] args) {
		print(new File(
				"C:/Temp/8565658FA6C187A602A5360A69F11933624DD9B5.dat.bak"),
				new File("C:/Temp/bdecoder.log"));
	}
}
